1. Field of the Invention
This invention relates to lead frame packages, and more specifically to leadless semiconductor packages and manufacturing methods thereof.
2. Description of the Related Art
Lead frame packages have been used for a long period of time in the IC packaging history mainly because of their low manufacturing cost and high reliability. However, as integrated circuits products move its endless pace toward both a faster speed and a smaller size, the traditional lead frame packages have become gradually obsolete for some high performance-required packages. Thus BGA (Ball Grid Array Packages) and CSP (Chip Scale Package) have emerged and become increasingly popular as a new packaging choice. The former has been widely used in IC chips that have higher I/Os and need better electrical and thermal performance than the conventional packages such as CPU and graphic chips. The latter has been widely used in mobile products of which the footprint, package profile and package weight are major concerns.
However, the lead frame package still remains its market share as a cost-effective solution for low I/O ICs. Traditional lead frame package has its limit of providing a solution for chip scale and low profile package due to the long inner leads and outer leads. Therefore, the semiconductor packaging industry develops a leadless package without outer leads such that both the footprint and the package profile can be greatly reduced. FIGS. 1 and 2 show a leadless package 10 wherein the leads 11a are disposed at the bottom of the package as compared to the conventional gull-wing or J-leaded type package. The die pad 11b of the leadless package 10 is exposed from the bottom of the package thereby providing better heat dissipation. Typically, there are four tie bars 11c being connected to the die pad 11b. The leadless package 10 includes a chip 12 sealed in a package body 13. The active surface of the chip 12 is provided with a plurality of bonding pads (not shown) electrically connected to the leads 11a via wire bonding.
Due to the elimination of the outer leads, leadless packages are featured by lower profile and weight. Furthermore, the leadless package 10 is also a cost-effective package due to its use of existing BOM (bill of materials). All the above-mentioned properties make the current leadless packages very suitable for telecommunication products such as cellular phones, portable products such as PDA (personal digital assistant), digital cameras, and IA (Information Appliance).
As the performance requirements for computers and other electronic apparatuses increase, the semiconductor devices operate at higher power and are manufactured at increased device densities. As a result, greater emphasis has been placed on the thermal performance of the semiconductor devices. However, currently available leadless packages fail to meet the high power dissipation requirements of automotive, industrial, and commercial applications.